An intense system of storms battered the US South on November 29 and 30, 2016. Numerous tornadoes were observed across the affected regions, five people were reported dead and numerous others injured.

A tornado was reported in Rosalie, northeast Alabama. According to Chuck Phillis, the Jackson County Sheriff, three people died and one was injured in a severe weather incident. At least 25 homes were damaged along with poultry operations in the county. At the same time, two people died due to severe weather outbreak in Tennessee, while nine more were injured.

Nine possible tornadoes were observed in Mississippi where widespread power outages and damage was reported. Louisiana and Tennessee also suffered severe storm conditions and several possible tornadoes accompanied by hail. Downed power lines and structural damage was reported across the affected areas.

Tornado watches were put in effect by the NSW on November 30, from the region of southeastern Louisiana through Mississippi, Alabama into northern Georgia and southeastern Tennessee. The area between the Mississippi and Tennessee valleys was in for heavy rainfall.

The emergency and NWS officials are currently in the process of estimating the damage caused by the storm outbreak.

According to the NWS forecast, heavy rainfalls accompanied by thunderstorms are expected in the lower Mississippi valley to the Northeast US on November 30. Several areas in the region of the lower Mississippi and Tennessee valley may also experience torrential downpour.

Storm, flood and tornadoes across Alabama and MississippiTens of thousands of people have lost power as severe weather rolled through the southern United States and turned deadly on Monday, January 2, 2017. As of early January 3 (UTC), at least 5 people have lost their lives. Authorities fear the death toll will rise and urge people to pay attention to the warnings and act accordingly.

A low pressure system brought severe thunderstorms to parts of the South on Monday, spinning off several tornadoes, flooding widespread areas and leaving more than 100 000 people without power.

The first line of storms storm hit parts of Texas around 05:00 local time, downing power lines, dropping small hail and sparking at least one house fire. At least 18 000 were without power. The second line of storms rolled in with the sunrise causing flash flooding.

The storms then headed east, causing significant damage to Louisiana, Mississippi, Alabama, and Florida. Much of the damage was caused by flash flooding after a series of storms soaked the region over the past week. Some regions received up to 180 - 230 mm (7 to 9 inches) of rain in just a couple of days.

In Louisiana, a possible tornado reportedly damaged several homes in LeCompte. Severe damage was also reported throughout Avoyaleles Parish, including houses that trees fell through and a building that lost its roof. More than 16 000 customers in the state were without power at one point.

In Alabama, four people were killed in a single home when a tornado hit the town of Rehobeth in the state's south and crashed a tree onto their mobile home.

In Florida, the body of a 70-year-old man was found floating outside his travel-trailer, the Walton County Sheriff's Office said. The death was ruled an accidental drowning.

Downed trees and damaged buildings were reported in at least 28 counties in Mississippi, 15 parishes in Louisiana and 15 counties in Texas, The Weather Channel meteorologist Danielle Banks said.

The study by researchers including Joel E. Cohen, a visiting scholar at the University of Chicago, finds the increase in tornado outbreaks does not appear to be the result of a warming climate as earlier models suggested. Instead, their findings tie the growth in frequency to trends in the vertical wind shear found in certain supercells—a change not so far associated with a warmer climate."What's pushing this rise in extreme outbreaks, during which the vast majority of tornado-related fatalities occur, is far from obvious in the present state of climate science," said Cohen, the Abby Rockefeller Mauzé Professor at Rockefeller University and Professor of Earth and Environmental Sciences at Columbia University, who conducted the research while a visiting scholar in UChicago's Department of Statistics.

Tornado outbreaks are large-scale weather events that last one to three days, featuring several thunderstorms and six or more tornadoes in close succession. In the study, published in the Dec. 16 issue of Science, the researchers used new statistical tools, including extreme value analysis—a branch of statistics dealing with deviations—to analyze observation-based meteorological estimates associated with tornado outbreaks together with National Oceanic and Atmospheric Administration datasets.

The researchers estimated that the number of tornadoes in the most extreme outbreak in a five-year interval doubled over the last half-century. This means that in 1965 the worst outbreak expected over five years would have had about 40 tornadoes, while in 2015 the worst outbreak expected over five years would have had about 80 tornadoes.

"Viewing the data on thousands of tornadoes that have been reliably recorded in the United States over the past half-century as a population has permitted us to ask new questions and discover new, important changes in outbreaks of these tornadoes," Cohen said.

To understand the increased frequency in tornado outbreaks, the researchers looked at two factors: convective available potential energy, or CAPE, and storm relative helicity, which is a measure of vertical wind shear.

Earlier studies had projected a warming climate would increase CAPE, creating conditions favorable to a rise in severe thunderstorms—and potentially tornado outbreaks. But Cohen and his colleagues found the increases in outbreaks were driven instead by storm relative helicity, which has not been projected to increase under a warming climate.

"Our study raises new questions about what climate change will do to severe thunderstorms and what is responsible for recent trends," said co-author Michael K. Tippett, an associate professor at Columbia University's Fu Foundation School of Engineering and Applied Science. "The fact that we didn't see the presently understood meteorological signature of global warming in changing outbreak statistics for tornadoes leaves two possibilities: Either the recent increases are not due to a warming climate, or a warming climate has implications for tornado activity that we don't understand."

At least four people were killed in southern Mississippi early Saturday when a destructive tornado roared through the Hattiesburg area, leveling homes, ripping off roofs and tossing trees into roadways across the region.

The city of Hattiesburg on Twitter and Forrest County emergency management confirmed the deaths. Forrest County Coroner Butch Benedict said two of the fatalities were in a trailer park. Numerous injuries were also reported. Nearby Lamar and Perry counties and the city of Petal were also hard hit.

The tornado ripped through the area just before 4 a.m., with strong winds that caused extensive damage in several blocks of Hattiesburg. As dawn rose, city residents awoke to find trees, massive limbs and poles wrapped in power lines littering the streets next to decimated and severely damaged homes. More than 12,000 were without power in the region.

"The total debris clean-up will be weeks at this point," said Lee Smithson, executive director of the Mississippi Emergency Management Agency.

High-risk declarations for severe weather are rare. The last such issuance was June 3, 2014, according to Weather.com and hasn’t occurred in winter since 2008 . Since 1984, 42 percent of tornado fatalities have coincided with such high-risk days, according to the Weather Channel’s Kathryn Prociv.

The region under high risk hasn’t seen such a designation in a decade, the website for U.S. Tornadoes reported.